The General Services Administration will announce the appointments of veteran transit official Mortimer L. Downey as a director and regional planning executive Marcel C. Acosta as an alternate director, GSA Acting Administrator Stephen R. Leeds said in a statement. The members -- the first of four federal appointees -- are expected to be seated at a scheduled board meeting Thursday.

The GSA had planned to announce all four appointees together, but "given the importance of what is going on" at Metro, it rushed to appoint Downey and Acosta in time for that meeting, said a GSA official who spoke on condition of anonymity.

The move to install the first federal representatives on Metro's board injects a fresh element of uncertainty into Metro operations as the agency struggles with historic budget deficits, a leadership vacuum in its executive ranks and widespread concerns about safety since the June 22 crash on the Red Line.

Metro General Manager John B. Catoe Jr. abruptly announced Jan. 14 that he will resign April 2. Officials said Metro is likely to be without a permanent top manager for the rest of the year as a national search for a replacement unfolds. Metro also announced last month that four senior managers would be leaving or be reassigned, including Catoe's top deputy and safety officer.

This week, the Metro board of directors leadership is also set to change hands: First Vice Chairman Peter Benjamin, a representative of Maryland, is expected to take over the chairmanship from Jim Graham of the District.

The role of the federal board members remains largely undefined, government and Metro officials said. "Never before has the federal government taken a role in governing any transit system in the United States. . . . This is entirely without precedent," Benjamin said. "As the next chair, I am going to have to integrate those roles when I don't have the foggiest idea what is going to happen."

The four federal appointees were mandated in legislation that authorized $1.5 billion in federal funds for safety-related capital investments in Metro over the next decade. But the legislation did not detail the role of federal board members, although it said at least one should be a frequent rider of the transit system.

The GSA chose the appointees after consulting with "a broad range of stakeholders both inside and outside the government and across the communities of interest," an official said. "The strengths we looked for were financial management, sustainability, expertise in transit operations and planning . . . and frequent riders of the Metro bus and Metrorail system."

"If the federal government is going to be kicking in $150 million a year, it deserves voting representation on the board," said Rep. Gerald E. Connolly (D-Va.).

Lawmakers who backed the legislation said their intent is for the new members to protect U.S. interests in the system, which carries a majority of the 300,000 local federal workers to and from their jobs each day.

"The federal government would like its employees to arrive at work on time, fundamentally alive," said Downey, 73, a transportation consultant who served as deputy secretary of transportation in the Clinton administration and director of the New York City transit authority, the largest in the nation. Downey, a resident of Vienna, has been "a devoted rider of the Metro system for over 20 years," according to a GSA statement. He "has been involved with the DC Metro system for over 30 years, helping to complete and fund the system as both a government official and an industry expert."